AC Raw Water Strainer Completely Fouled with Pea Sized Oysterss

Yesterday, when I noticed my AC discharge water flow suddenly went to a trickle and ambient temp to air discharge dropped to 8 degrees F, I proceeded to pull the strainer for a periodic clean out.

What I found was shocking. Usually when I check strainers, I find a few shells, bits of seaweed, but nothing too bad. This time the stainer was packed to the brim with tiny little clams or oysters no bigger than a pea. It was packed so tight, I had a chore removing the basket from the housing. Much to my distress, it was apparent many of the little buggers made it through the basket to the clean water side.

What a fun project, sweating near the bilge cleaning as much of the strainer as I could reach.

Opened the seacock with lid off strainer and observed good flow. Put it all back together and turned on AC. Flow was a bit improved but not where it should be. Temperature differential was 12F, better but not the 13-15F I am used to seeing. Conclusion - I have scale or oysters growing in my system.


So, what to do? I think what we may have here is beyond the capabilities of vinegar, CLR or Barnacle Buster. I'm thinking of bringing out the big guns like muriatic acid.

Suggestions are welcome. If muriatic is the way to go, I'd appreciate input on dilution and contact time.

btw, I'm in South Florida so just opening a window and turning on a fan is NOT an option.

CLR needs more time than stronger acids. Also is less likely to hurt things. It's just time.

I've soaked systems overnight and had clear flow the next day.

They grow in the lines too. Usually worst after a haul out because they die and clog the lines. Especially at manifolds Look like mini mussels about 1/4” long.

Sometimes back flushing hoses with pressure work but make sure to put the end of the hose in a bucket otherwise you really just moving them around the system.

Quote:

---

Originally Posted by Passages

Yesterday, when I noticed my AC discharge water flow suddenly went to a trickle and ambient temp to air discharge dropped to 8 degrees F, I proceeded to pull the strainer for a periodic clean out.

What I found was shocking. Usually when I check stainers, I find a few shells, bits of seaweed, but nothing too bad. This time the stainer was packed to the brim with tiny little clams or oysters no bigger than a pea. It was packed so tight, I had a chore removing the basket from the housing. Much to my distress, it was apparent many of the little buggers made it through the basket to the clean water side.

What a fun project, sweating near the bilge cleaning as much of the strainer as I could reach.

Opened the seacock with lid off stainer and observed good flow. Put it all back together and turned on AC. Flow was a bit improved but not where it should be. Temperature differential was 12F, better but not the 13-15F I am used to seeing. Conclusion - I have scale or oysters growing in my system.


So, what to do? I think what we may have here is beyond the capabilities of vinegar, CLR or Barnacle Buster. I'm thinking of bringing out the big guns like muriatic acid.

Suggestions are welcome. If muriatic is the way to go, I'd appreciate input on dilution and contact time.

btw, I'm in South Florida so just opening a window and turning on a fan is NOT an option.

---

I'd be real careful about overdoing it. The white vinegar is safest, but takes maybe all day. The BB takes and hour or so. Either way, the hoses from the seacock to the supply side of your pump won't get done when you hook up your loop. I'd get all the water out of those and back fill with vinegar. Let it sit all day or all night if you can stand it. Or, just replace those hoses.

But, the most important advice is how to prevent. I fill my baskets with bromine pellets and have zero oyster, mussel, barnacle or other hard critter issues. If you find any of those in there, they'll be soft and dead and unable to attach. This time of year I'll have to replenish pellets every 3-4 weeks in Charleston waters. I've been filling all my baskets with bromine for three years now and they stay clean. Walmart used to carry bromine in pellets, but I'm not certain now. I bought a years supply because it appeared they were discontinuing.

^Bromine tablets. Brilliant! I should be able to pick them up at a pool/hot tub shop. If bromine is not available, I suspect chlorine tablets would also work.

Regarding the short term issue, yes strong acids worry me a bit. Speed is important though. As a full time liveaboard in South FL, 24 hours without AC will make for a fairly sleepless night.

I'm hoping there is something out there which is safe on metal but quickly tears the heck out of hard shell critters. Anyone? Bueller?...Bueller?

Isolate a system at a time so you only lose one unit while cleaning it.

Quote:

---

Originally Posted by Boatsb

Isolate a system at a time so you only lose one unit while cleaning it.

---

What Scott said.

Last year I had the small muscles in all 4 ac units. Tried flushing with fresh water first to no avail. Ended up buying several gallons of Barnacle Buster concentrate, and worked great.

I was worried about the smell, so I put a 10 gallon polly barrel on the dock, and 2 garden hoses going into the pump room. Put ball valves on each hose to close so I could change to other units easily. I used a march pump to circulate the acid. I Isolated each unit like Scott stated, and ran the mixture for about 4 hours each ac unit. I could fill 2 solo cups with the critters that came out of each unit. In over 25 years of owning Hatteras', this is the first time I have ever had this issue. First time I have ever seen these little green muscles.

The gases of the mixture were not as bad as I thought they would be, so this fall I am assembling a smaller bucket that will fit in the pump room to make the chore easier. I was using over 100 feet of garden hose from the dock through a deck hatch and into the boat. This took an extra amount of product just to fill the lines.

I do not have sea strainers to use tablets, just screens. On My last 2 Hatts, I had the sea strainers, and I did use the Bromine tablets, and maybe that is the reason this was never an issue. Could be I picked them up going through Lake Okeechobee. My screens are small, so they had to come in as larvae.

My March pump was external of the poly barrel, and used a nylon thru hull to connect from the bottom of the barrel to the pump. Return line just dumped over the top. So no wear issues to the pump. Another boat owner made one out of a 6 gallon bucket, and used a submersible pump. Worked good, he had no issues, but I have not seen it this year to vouch for longevity. When I inspected my circulation hoses, they were in there also, so I just replaced the difficult ones. They were also in the supply lines coming in from the thru hulls going to the pumps, and yes they were in the pumps as well.


Hope this helps,
Have a great week.

Tim

Hi Tim,

You can save a ton by just using phosphoric acid (http://www.kleanstrip.com/product/phosphoric-prep-etch) which is the active ingredient in BB. I mix it 3 qts. acid to 17 qts. water for 5 gallons. I think that's between 10-12% acid. It's $8/gallon in paint dept. at Home Depot versus lots more of BB. I use the same formula for motors as well as AC loop, though I generally only run for 30 minutes in ACs.

As for the fumes, I'm probably toxic from all I've been exposed to in life. I've never noticed anything worth mentioning in that dilution. I don't own 100' of hose, let alone twice that. I just installed quick connects and enough hose (maybe 5') to reach a 5 gallon bucket with a 110V submersible pump. I've also found that the mix comes out pretty clean after 45 minutes to and hour.

Attachment 26618
Helpful hint #1: Raise the output line above the piping you are cleaning to purge air and ensure solution gets to 100% of the pipes/hoses to be cleaned.

Helpful hint #2: If you're doing a motor, make sure you block the small water line going to (if you have them) your dripless seals or you'll be headed back for more chemical.

Helpful hint #3: Let solution stand in raw water intake hoses for an hour or two so as to contact seacocks. If you have hard to open valves you may have one finger valves pretty soon. I started out with Aslan with a cheater on the mains; now it's finger tips. That's a $3,500 (estimate 3 years ago) savings from recommended replacement.

Thanks Robert,

Taking your advice on the Home Depot remedy. Already have valves and quick disconnects purchased to make this process easier in the future. I am rebuilding my Raw Water pumps on the mains right now, and after seeing the scale buildup on the salt and fresh water sides I will be putting quick disconnects on the mains as well.

Havn't even started on the generators yet. Kind of worried what I will find there. Too many tasks, not enough weekends..

Here in Florida, the AC's had to come first. The older I get, the less I can tolerate the heat.

Take Care,
Tim

Good deal. Don't forget to remove all zincs or your solution will do it for you.